The use of automated drilling methods is becoming increasing common in drilling subterranean wellbores. Such methods may be employed, for example, to control the speed and/or the direction of drilling. Automated methods may also be employed during measurement while drilling (MWD) or logging while drilling (LWD) operations to collect borehole and/or formation related data during drilling. While such methods are commonly used in the drilling industry, their utility may be improved by a downhole determination of the drilling state. For example, MWD and LWD tools may be configured to collect data only during certain drilling states (such as while rotary drilling) or a telemetry tool may be configured to automatically transmit data to the surface in certain drilling states.
The drilling state is generally known at the surface. For example, it is known whether the rig is being run it, tripping out, off bottom, rotary drilling, reaming, and the like. Moreover, surface equipment may be updated with changes to the drilling state. However, downhole tools are generally disconnected from the surface and are therefore “unaware” of the drilling state. While the drilling state may be transmitted from the surface to the bottom hole assembly (BHA), such transmission requires sufficient bandwidth and consumes valuable rig time (especially if a transmission is required after each change to the drilling state). A downhole determination of the drilling state may be timelier and therefore allow for more efficient automated control of various downhole tools. As such there is a need in the art for a method of making a downhole determination of the drilling state during a drilling operation.